From 455d4f41fb1c2bf48645b4904a8ee293272c90db Mon Sep 17 00:00:00 2001
From: Jorropo <jorropo.pgm@gmail.com>
Date: Tue, 7 Apr 2026 11:57:56 +0200
Subject: cmd/compile: run CondSelect into math rules on all arches

Fixes #78558

I've also added tests to make sure PPC still generate ISEL when
the constant isn't 1.
This is to make sure we aren't generating a sequence that wouldn't
work right now.

But it does not mean we couldn't try to optimize other constants
on PPC64 if a fast sequence exists; for example like arm64's
inline register shifts.

Change-Id: Ic241d593149b7a11533948f5d4c52db357cc134f
Reviewed-on: https://go-review.googlesource.com/c/go/+/763340
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jayanth Krishnamurthy <jayanth.krishnamurthy@ibm.com>
Reviewed-by: Paul Murphy <paumurph@redhat.com>
---
 src/cmd/compile/internal/ssa/rewrite.go | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'src')

diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index 008767f19c..eefabfba2f 100644
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -2834,6 +2834,9 @@ func rewriteCondSelectIntoMath(config *Config, op Op, constant int64) bool {
 				return true
 			}
 		}
+	default:
+		// TODO: fine tune for other architectures.
+		return constant == 1
 	}
 	return false
 }
-- 
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